おじいちゃん

The affectionate, informal form of 祖父(そふ) (grandfather) or おじいさん. The ちゃん suffix makes it warmer and more childlike than おじいさん.

Formality scale

• 祖父(そふ) — formal/written; used when referring to one's own grandfather in formal contexts
• おじいさん — polite; used for someone else's grandfather or an elderly man
• おじいちゃん — informal/affectionate; used within the family or for a familiar elderly man
• じいちゃん — very informal; casual, often used by boys and men

Similar words

• おばあちゃん — grandmother; grandma; old woman (the female equivalent)
• おじいさん — grandfather; old man (polite form)
• 祖父(そふ) — grandfather (formal)
• 老人(ろうじん) — elderly person (neutral/formal)

Usage

When referring to your own grandfather to outsiders, use 祖父(そふ) in formal situations. When speaking to or about someone else's grandfather, use おじいさん or おじいさま. おじいちゃん is for family use or when speaking affectionately. Calling an unknown elderly man おじいちゃん can sound either friendly or condescending depending on context.